Stabilization of polymerizable heterocyclic nitrogen compounds



United States Patent V STABILIZATION 0F POLYMERIZABLE HETERO- CYCLIC NITROGEN COMPOUNDS Warren L. Smith and Mack- F. Potts, Bartlesville, 0kla., and Paul S. Hudson, Iowa City, Iowa, assignors to Phillips Petroleum Company, a-corporation of Delaware No Drawing. Application November 3, 1952, Serial No. 318,514

13 Claims. (Cl. 260-290) This invention relates to'the'stabilization' of polymerizable compounds. In one of its-aspects this invention relates to the stabilization of polymerizable heterocyclic nitrogen compounds under storage and'handling conditions; and during'distillation, or at" elevated temperatures. In' another ofits more specific aspects, this inven'tion relates' to amethod for preventing loss of heterocyclic nitrog'enfcompounds due to polymerization.

It iswell-knownthatunsaturated, polymerizable heterocy'clie nitrogen compounds tend to polymerize during storage'and various h'andling conditions, especially during distillation, and consequently yield and recovery ofthese compounds are often times considerably diminished due to this unwanted and undesirable polymerization. Also, besides reducing yields and recovery of these polymerizable heterocyclic nitrogen compounds, often the polymerized material adversely afiects the reaction wherein these polymerizable compounds 'are employed as reactants, as well as the products which are derived from these reactions.

Ea'ch ofthe objects of this invention will be obtained by at least one ofthe aspects of this invention.

It is'a'n' object or this invention toprw'enfand/o'r inhibit the polymerization of polymerizable heterocyclic nitrogen compounds durin'g'storageand other handling situations. It'is another objectof this invention'to inhibit the polymerization of these materials at elevatedtemp'e'ratures and especially during distillation. It is another ob ject of this invention to provide polymerization inhibited compositions comprising a polymerizable heterocyclic nitrogen compound. Yet another object of this invention is to provide a polymerization: inhibited composition comprising a vinyl-substituted pyridine.

Other and further objects andadvantages of this invention will be apparent to those skilled in the art upon study of the accompanying; disclosure.

In accordance with this invention, we have found that these heterocyclic nitrogen compounds can be stabilized against polymerization by addition thereto of a naphthylamine sulfonic acid. 7 Certain naphthylamine sulfonic acids, i. e., those Whichcontain either oneor two amino groups in the 1 and/or 2 positions in the naphthalene structure and either one or two- -SO3H groups in one and/ or two of the 5, 6, 7, and 8 positions of the naphthalene structure, such as l-naphthylamineJ-sulfonic acid are efiective stabilizers. It has also been found that compounds of similar type, but with the amino and sulfonic acid groups in dili erent positions inthemolecule with respect to each other, such as Z-naphthylamine-l-sulfonic acid, are ineffective as stabilizers or polymerizationinhibitors for these heterocyclic nitrogen compounds.: I

Naphthylamine sulfonic acids which areapplicable-are compounds which can be represented by the formula 2,748,131 Patented May'29; 1956 wherein R1 issele'ete'd from the "group -c'onsisting of hydrogen or amino groups and with at least one R1 being an amino group, and R2 is selected from the group consisting of hydrogen or 4O3Hg'roupsand with at least one but not more than two -SO3H groups being present. EX- amples of compounds which are applicable include l-naphthylamine 5 sulfonic acid, 2-naphthylamine-5- sulfonic acid, 1-naphthylamine-5,6 disulfonic acid, 1,2 diaminonaph'thalened,6-disulfonic acid, and Z-naphthylan'iine-6-sulfonic acid. 7

These naphthylamine sulfonic acids' are effective as polymerization inhibitors over a wide range of tempera-- tures from below and about 40 F. up to and about 400 F. The amount ofthe stabilizing agent which need be added toinhibit polymerization varies with the type of polymerizable heterocyclic-nitrogen compound to be inhibited andthetime and temperature under which it is desired to eifect stabilization. Often a trace of the naphthylamine sulfonic acidissufiicient to prevent undesired polymerization. We usually use an amount in the range of- 0.001 to" 5.0 per cent by weight, preferably from 0.05 to 1.0 per cent-by weight, based on the amount of the polyrne'rizable heterocyclic nitrogen compound- Larger amounts; even as much as 10 per cent by weight and higher can be" used-if desired,-although=under most circumstancesthis is not necessary. These stabilizing agents'a-re-eifective inanhydrous systems as well as in: systems where water is present.-

These naphthyla'mine sulfonic aeids',"in order to be especially efiective, should'p'referably be-in intimate con-- tact with the material to be stabilized. As these naphthyl amine sulfonic acids are, in general, only slightly soluble in the polymerizable heterocyclic nitrogen compounds,. they are generally added as fine powders after which the mixture is stirred and/ or warmed; The stabilizing agent maybe added batchwise or continuously as the heterocyclic nitrogen compound is produced.

The recovery of the naphthylamine sulfonic acids from the polymerizableheterocyclic nitrogen compounds with; which-it is admixed'isrelati-vely simpleand easily effected. After storage, handling, or shipment of the stabilized ma terial, the stabilizing" agent can be easily and readily separated" and recovered either by distillation, preferably under reduced pressure," or: by any other convenient. method.

The polymerizabl'e heterocyclic nitrogen compounds.- whichcan beinhibited against polymerization by these naphthylamide 'sulfonic a'cids'itf accordance with this in vention includeithe polymerizable heterocyclic nitrogen] com ounds of the pyridine and quinoline' (including iso-- quindline') 1 series and thenuclear (ring) alkyl-substituted. These polymerizable heterocyclic:

derivatives thereof. nitrogen compounds are 'tlfosec'ontaining a OHF'Chgroup'where' R isahyd'rQgen atom or a methyl roup- One ort'wo vinyl groups maybe present, and also alkyl groups may be present attached to the ring as long as there are not more than 12 carbon atoms in these alkyl groups-. Typical heterocyclic nitrogen compounds which are applicable in the practice of this invention include thevinyl substituted pyridines and the vinyl-substituted quinomerizable nitrogen compound such as vinyl substituted pyn'dines, quinolines or isoquinolines are applicable in the practice of this invention. Other polymerizable heterocyclic nitrogen compounds which can be stabilized by following the teaching of this invention include the Example I A run was made using 1-naphthylamine-5-sulfonic acid as an inhibitor for the polymerization of Z-methyl-S-vinylpyridine by adding 0.3 per cent by weight of this compound to Z-methyl-S-vinylpyridine and heating the mixture in an atmosphere of nitrogen for 24 hours at 185 F. The unreacted 2-methyl-5-vinylpyridine was removed by vacuum distillation at a pressure less than 1 mm. Hg. The polymer which remained was weighed and the per cent 2-methyl-5-vinylpyridine polymerized was calculated. A second run was made in which no additive was present. The following results were obtained:

Percent Z-Methyl- 5 Vinylpyridine Polymerized Additive l-Naphthylamiue-S-sulfon1c acid None One run was made using Z-naphthylamine-l-sulfonic acid as a polymerization inhibitor for 2-methyl-5-vinylpyridine using 0.3 weight per cent of the additive based on the Z-methyl-S-vinylpyridine, The mixture was heated in an atmosphere of nitrogen for 24 hours at 200 F. 2-naphthylaminel-sulfonic acid is ineffective as a polymerization inhibitor as evidenced by the fact that the sample became very viscous and was similar in appearance to a run in which Z-methyl-S-vinylpyridine was heated under similar conditions in the absence of an additive.

Example 11 A run was made similar to those in Example I using Z-naphthylamine-S-sulfonic acid as a polymerization in hibitor in a sample of Z-methyl-S-vinylpyridine containing per cent by Weight of water. The result was as follows:

Percent Z-Methyl- 5-Vinylpyridine Polymerized Additive 2-Na phthylamine-5-sultonle acid 3. 94

As many possible embodiments may be made of this invention without departing from the scope thereof, it is to be understood that all matter herein set forth is to be interpreted as illustrative and not in a limiting sense.

We claim:

l. A polymerizable heterocyclic nitrogen base selected from the group consisting of compounds having the formula l ow-h- (R')1-n =0 i) and R a)... (has.

where n is an integer selected from the group consisting of 1 and 2, R is selected from the group consisting of H and CH3, and R is selected from the group consisting of H and alkyl groups, not more than 12 carbon atoms being present in the total of said R groups, said heterocyclic nitrogen base being stabilized by the addition of a stabilizing amount of a naphthylamine sulfonic acid selected from the group consisting of compounds having the formula wherein R1 is selected from the group consisting of hydrogen and amino groups, at least one R1 being an amino group, and R2 is selected from the group consisting of hydrogen and -SOaI-I groups, at least one and not more than two SO3H groups being present.

2. A polymerizable heterocyclic nitrogen base selected from the group consisting of compounds having the where n is an integer selected from the group consisting of 1 and 2, R is selected from the group consisting of H and CH3, and R is selected from the group consisting of H and alkyl groups, not more than 12 carbon atoms being present in the total of said R groups, said heterocyclic nitrogen base being stabilized by the addition of from 0.001 to 5.0 per cent by weight of a naphthylamine sulfonic acid selected from the group consisting of compounds having the formula W wherein R1 is selected from the group consisting of hydrogen and amino rasps; atleast oneR1 being an amino group, and R2 is selected from the m-1 consisting;- of hydrogen and-SO3H- groups,--at lca'stoiie and'not'ni'ore than two SO3H groups being prese'nt-l 3. 2-methyl-5-vinylpyridine stabilized: by the addition of a stabilizing amount ofa naphthylaminesulfonic acid selected from the group consisting of" conipt iufids having the formula 1 wherein R1 is selected from the group consisting of hydrogen and amino groups, at least one R1 being an amino group, and R2 is selected from the group consisting of hydrogen and -SO3H groups, at least one and not more than two SO3H groups being present.

4. Z-methyl-S-vinylpyridine stabilized by the addition of from 0.001 to 5.0 per cent by weight of a naphthylamine sulfonic acid selected from the group consisting of compounds having the formula R1 wherein R1 is selected from the group consisting of hydrogen and amino groups, at least one R1 being an amino group, and R2 is selected from the group consisting of hydrogen and --SO3H groups, at least one and not more than two SO3H groups being present.

5. 2-methyl-5-vinylpyridine stabilized by the addition of 0.001 to 5.0 per cent by weight of l-napthylamine-S- sulfonic acid.

6. Z-methyl-S-vinylpyridine stabilized by the addition of 0.001 to 5.0 per cent by weight of 2-naphthylarnine-5- sulfonic acid.

7. 2-vinylpyridine stabilized by the addition of a stabilizing amount of a naphthylamine sulfonic acid selected from the group consisting of compounds having the formula 1 wherein R1 is selected from the group consisting of hydrogen and amino groups, at least one R1 being an amino group, and R2 is selected from the group consisting of hydrogen and SO3H groups, at least one and not more than two -SO3H groups being present.

8. 2-vinylpyridine stabilized by the addition of from 0.001 to 5.0 per cent by weight of a naphthylamine sulfonic acid selected from the group consisting of compounds having the formula wherein R1 is selected from the group consisting of hydrogen and amino groups, at least one R1 being an amino group, and R2 is selected from the group consisting of 6 hydrogen and groups,-at least oneand not-morethan two-SO:;I-I groups being present.

9LA process for inhibiting: the polymerization ofv a compound selected from the group consisting of cornpounds having the formula and where n is an integer selected from the group consisting of 1 and 2, R is selected from the group consisting of H and CH3, and R is selected from the group consisting of H and alkyl groups, not more than 12 carbon atoms being present in the total of said R groups, which comprises adding to said compound a polymerization inhibiting amount of a naphthylamine sulfonic acid selected from the group consisting of compounds having the formula wherein R1 is selected from the group consisting of hydrogen and amino groups, at least one R1 being an amino group, and R2 is selected from the group consisting of hydrogen and -SO3H groups, at least one and not more than two -SO3H groups being present.

10. A process for inhibiting the polymerization of 2- methyl-S-vinylpyridine which comprises adding to said 2- methyl-S-vinylpyridine from 0.001 to 5 per cent by weight of a naphthylamine sulfonic acid selected from the group consisting of compounds having the formula lia R1 wherein R1 is selected from the group consisting of hydrogen and amino groups, at least one R1 being an amino group, and R2 is selected from the group consisting of hydrogen and --SO3H groups. at least one and not more than two SO3H groups being present.

12. A process for inhibiting the polymerization of 2- methyl -S-vihylpyridine which comprises adding to said 2- methyl-S-vinylpyridine from 0.001 to 5.0 per cent by Weight of 1-naphthy1amine-5-sulfonic acid.

13. A process for inhibiting the polymerization of 2- methyl-S-vinylpyridine which comprises adding to said 2- methy1-5-viny1pyridine from 0.001 to 5.0 per cent by weight of 1-naphthylamine-5-sulfonic acid.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Alekeenko: Chem. Abst., vol. 40, col. 2675 (1946). Frank et aL: JACS, vol. 68, p. 908 (1946). 

1. A POLYMERIZABLE HETEROCYCLIC NITROGEN BASE SELECTED FROM THE GROUP CONSISTING OF COMPOUNDS HAVING THE FORMULA 